The research, led by Carollina Mariga and colleagues at the Federal University of Santa Maria in Rio Grande do Sul, Brazil, set out to answer two questions at once: whether adjunctive Cannabis oil could improve control of recurrent clinical signs in dogs whose oclacitinib treatment had been unsatisfactory, and whether the cannabinoid supplement could allow a structured reduction of the conventional drug without clinical relapse. Sixteen dogs with a confirmed diagnosis of atopic dermatitis were enrolled, each previously treated with oclacitinib without satisfactory improvement. Food allergy had been excluded through an 8-to-12-week hypoallergenic elimination diet, and flea bite dermatitis was ruled out, following established diagnostic criteria.

The study design was a prospective, placebo-controlled, repeated-measures protocol in which every dog moved through the same fixed sequence of four stages. At T0, the animals received oclacitinib alone at individualized doses ranging from 0.2 to 1.1 mg/kg once daily, deliberately adjusted to leave a clinically detectable level of pruritus so that owners could perceive any treatment-related change. During the next 30 days, T30, the dogs received an oral placebo of mineral oil — tinted with artificial yellow food coloring to mimic the appearance of Cannabis oil — alongside full-dose oclacitinib. At T60, the placebo was replaced by Cannabis oil delivering 2.0 mg/kg of cannabidiol twice daily, still combined with full-dose oclacitinib. Finally, at T90, the cannabinoid oil was maintained while the oclacitinib dose was reduced by 50 percent. Because each animal served as its own control across all phases, the design reduced the interindividual biological variability that plagues cannabinoid research, where endocannabinoid tone differs markedly between individuals and tissues.

Assessment relied on two blinded instruments. A veterinary dermatologist scored skin lesions using the Canine Atopic Dermatitis Extent and Severity Index, CADESI-4, adapted to include the ventral cervical region, while owners rated itching on a simple zero-to-five behavioral scale at every visit. Crucially, both the dermatologist and the owners were unaware of whether the animal was receiving placebo or Cannabis oil at any given phase, and the dermatologist was not informed of the study design or treatment sequence. Fourteen of the sixteen dogs completed all stages through T90; two were withdrawn before the final month because of deep secondary skin infections requiring systemic therapy, diagnosed clinically and by cytology.

The statistical picture was nuanced. CADESI-4 scores, analyzed with generalized linear mixed models, showed no statistically significant effect of time, with estimated marginal means of 4.65 at baseline, 5.13 during placebo, 2.74 during Cannabis treatment, and 3.59 after the oclacitinib reduction. The primary planned contrast between the placebo and Cannabis phases did not reach significance, and after Holm adjustment no pairwise comparison was significant. Pruritus, however, told a different story. A cumulative link mixed model accounting for the ordinal nature of the itch scale and the repeated measurements found a significant effect of time, with mean scores falling from 3.44 at baseline to 3.00 during placebo, 2.31 during Cannabis treatment, and 2.42 after the dose reduction. The direct placebo-versus-Cannabis comparison again fell short of significance, but the comparisons against baseline were striking: itch odds were significantly lower at T60 (p = 0.0013) and at T90 (p = 0.0065) than at T0, indicating lower cumulative odds of being in higher pruritus categories once cannabinoid therapy began.

Perhaps the most clinically intriguing finding emerged at the end of the protocol. When Cannabis oil was interrupted after T90 while the dogs remained on half their original oclacitinib dose, nine of the fourteen animals resumed scratching within a week — four on the second day, two on the third, one on the fourth, and two on the seventh. The remaining five dogs stayed stable for the full seven days without cannabinoid supplementation. Nine owners, or 56.25 percent, chose to continue Cannabis treatment after the study concluded. Together with the maintained pruritus scores during the 50 percent oclacitinib taper, these observations support the hypothesis that adjunctive cannabinoids may exert a drug-sparing effect, allowing meaningful dose reductions of an expensive targeted therapy without loss of itch control.

The biological plausibility of an antipruritic effect rests on the endocannabinoid system, a homeostatic regulator expressed throughout the layers of the skin and in immune cells. Cannabinoid receptor type 1 and type 2 expression is increased in the skin cells of atopic dogs, and experimental work in genetically modified mice shows that deleting CB1 receptors in primary sensory neurons exacerbates inflammation and pruritus, promoting substance P production and mast cell accumulation in the dermis, while CB2 deletion worsens psoriasiform dermatitis and itch. Cannabidiol itself demonstrates broad immunosuppressive potential by downregulating the Janus kinase/signal transducer and activator of transcription pathway — the very pathway oclacitinib targets — and inhibiting key activating cytokines including interleukin-6, interleukin-2, interferon-gamma, and tumor necrosis factor, while also disrupting interconnected cascades such as PI3K-Akt and MAPK.

The formulation used was a full-spectrum, CBD-rich oil containing 73.7 percent CBD by relative proportion of total cannabinoid mass, along with 2.11 percent delta-9-tetrahydrocannabinol, 2.05 percent cannabichromene, 1.85 percent cannabigerol, and smaller amounts of cannabidivarin, cannabigerolic acid, and cannabinol, plus terpenes such as caryophyllene, humulene, nerolidol, guaiol, and bisabolol. The authors argue that this chemical complexity — the so-called entourage effect — may enable multitarget action on inflammatory pathways including MAPK, NF-kB, the NLRP3 inflammasome, and JAK1/STAT6 signaling in skin cells. In vitro studies suggest that cannabichromene downregulates master inflammatory signaling by inhibiting NF-kB and MAPK and suppressing TNF-alpha, interleukin-1 beta, and inducible nitric oxide synthase, while cannabigerol provides immunomodulation through CB2 receptor engagement, PPAR-gamma and Nrf2 activation, and direct inhibition of COX-1, COX-2, and iNOS. The oil underwent laboratory analysis confirming its cannabinoid and terpene profile and the absence of contaminants such as heavy metals, mycotoxins, pesticides, and solvent residues.

The results align closely with a prior prospective, randomized, double-blinded, placebo-controlled study by Loewinger and colleagues, in which 32 atopic dogs treated with a CBD/CBDA mixture showed a significant reduction in pruritus that nonetheless failed to reach significance against placebo, and no improvement in CADESI-4 lesion scores. A retrospective report by Mogi and colleagues, in contrast, described improvements in both itch and lesions in eight dogs treated with CBD-rich oil, though without a control group and with gradually escalating doses. The authors also note that their cohort presented with considerably lower baseline lesion scores than in their own earlier pre-study, reflecting a deliberate choice to include dogs across the full clinical spectrum seen in routine practice — a decision that may have reduced the sensitivity of CADESI-4 to detect treatment-related improvement, since several animals had low or null baseline scores.

Safety findings were reassuring but instructive. During the placebo month, 62.5 percent of dogs experienced at least one adverse clinical sign, including drowsiness, soft stools, and vomiting; during the Cannabis introduction month, 68.75 percent did, with drowsiness the most frequent complaint; and during the final maintenance month, 35.71 percent. All episodes were mild, transient, and self-limiting. Notably, roughly one in five animals reported drowsiness, vomiting, or soft stools even while receiving only mineral oil and food coloring — a pattern the authors attribute at least partly to the caregiver placebo effect, in which owners attribute expected adverse effects to treatment after being informed of study procedures, though spontaneous gastrointestinal signs or effects of the placebo formulation itself remain possible. No relevant behavioral alterations were identified during cannabinoid therapy, consistent with previous work showing that CBD administration does not affect daily voluntary activity in healthy dogs.

The authors are candid about the limitations. The sequential design confounds treatment with time, so observed changes cannot be cleanly separated from natural disease fluctuations, regression to the mean, or observer expectation bias. Pruritus was measured with a simple owner-reported scale rather than the validated Pruritus Visual Analog Scale, the sample was small, and seasonal variation in pruritus was not formally investigated. The CBD-rich formulation, constrained by Brazilian regulations limiting THC content in marketed products to 0.3 percent, prevents evaluation of the potential contribution of higher THC levels and other minor cannabinoids. Still, the study is, to the authors’ knowledge, the first to report the combination of Cannabis oil and oclacitinib in dogs with atopic dermatitis and to provide preliminary observations of a potential oclacitinib-sparing effect. The findings do not support recommending Cannabis as a first-line treatment, but they raise an exploratory hypothesis that earlier introduction of cannabinoid therapy may offer clinical benefits before chronic inflammatory changes become fully established — a question that now demands randomized controlled trials to establish the specific contribution of Cannabis oil to clinical improvement and to consolidate its place in multimodal therapy for this lifelong disease.

Subject of Research: Clinical observations during adjunctive Cannabis treatment and subsequent oclacitinib dose reduction in dogs with atopic dermatitis

Article Title: Clinical observations during adjunctive Cannabis treatment and subsequent oclacitinib dose reduction in dogs with atopic dermatitis

Article References: Mariga, C., Silva, F. C. D., Schiefler, O. H. D. M., Amazonas, E., Mateus, A. L. S. S., Schmidt, C., & Filho, S. T. L. P. (2026). Clinical observations during adjunctive Cannabis treatment and subsequent oclacitinib dose reduction in dogs with atopic dermatitis. Frontiers in Allergy, 7, Article 1852631. https://doi.org/10.3389/falgy.2026.1852631

Image Credits: AI Generated

DOI: 10.3389/falgy.2026.1852631

Keywords: canine atopic dermatitis, cannabidiol, oclacitinib, endocannabinoid system, veterinary dermatology, pruritus, cannabis oil, multimodal therapy, CADESI-4, drug-sparing effect, Clinical, observations

Papillomaviruses are small, circular, double-stranded DNA viruses that infect a wide range of vertebrates, from humans and cats to horses and fish. In dogs, infections are usually subclinical, but certain viral types have been linked to hyperplastic lesions and, more rarely, to cancer. Thirty-three distinct canine papillomavirus types have been catalogued to date, organized into three genera: Lambdapapillomavirus, Taupapillomavirus, and Chipapillomavirus. These viruses are associated with a spectrum of epithelial disease, including oral and cutaneous papillomatosis, pigmented plaques, and squamous cell carcinomas.

Pigmented plaques in dogs are generally small, flat to slightly raised, darkly pigmented lesions that remain localized, most often affecting breeds such as pugs and miniature schnauzers. In a subset of cases, however, the plaques spread widely across the skin, and malignant transformation into squamous cell carcinoma has occasionally been documented. The mechanisms driving this progression remain incompletely understood, although the presence of viral oncogenes and host factors are thought to contribute. Until now, documented papillomavirus co-infections in dogs had been limited to interactions between CPV1 and CPV2, members of the Lambdapapillomavirus and Taupapillomavirus genera.

The patient in this report was referred to a veterinary dermatology service in Porto Alegre, Brazil, with cutaneous lesions that had been slowly progressing for five years. Prior treatments, including oral and injectable corticosteroids, monthly afoxolaner, and topical moisturizers, had met with limited success. Blood work was unremarkable and the dog was otherwise healthy. Physical examination revealed multiple pigmented plaques with black and yellow coloration on the darker skin of the trunk and limbs, erythematous crusted plaques on the lighter skin of the abdomen and neck, generalized comedones, and scaling. Several ulcerated lesions were also present, including a large one on the right side of the neck and two smaller ones on the flanks.

Under general anesthesia, the dog underwent skin biopsy. Histopathological examination of the pigmented plaques revealed an endophytic scalloped proliferation of spinous layer keratinocytes with hypergranulosis, hyperpigmentation, and orthokeratosis, consistent with canine pigmented viral plaque. The ulcerated neck lesion, by contrast, showed a nodular infiltrative transformation with large polygonal tumor cells forming trabeculae and keratin pearls, marked cellular atypia, and aberrant mitotic figures, supporting a diagnosis of moderately well-differentiated squamous cell carcinoma. A third sample from a flank lesion was classified as carcinoma in situ. Although the team could not confirm whether the carcinoma arose directly from a pre-existing plaque, it developed in a previously affected region of skin.

To characterize the viruses, the researchers turned to multiply primed rolling-circle amplification coupled with high-throughput sequencing, an approach well suited to circular viral genomes. The method enriches circular DNA and, unlike conventional PCR with degenerate primers, can recover divergent or co-infecting papillomavirus types without bias. Sequencing on an Illumina MiSeq platform generated more than 4.3 million paired-end high-quality reads. Of these, roughly 3.9 million were classified as CPV9 and about 409,000 as CPV8, and de novo assembly yielded two complete, distinct circular genomes, named CPV9_LMM and CPV8_LMM, measuring 8,396 and 7,953 base pairs respectively.

The two genomes showed average sequencing depths of 20,509-fold and 4,412-fold, ensuring reliable identification of every genomic region. Each carried the typical papillomavirus gene set, including the early genes involved in replication and cell transformation and the late genes encoding structural proteins for virion assembly, along with a non-coding upstream regulatory region controlling gene expression. Nucleotide identity with reference genomes reached 99.64 percent for CPV9 and 99.85 percent for CPV8, and phylogenetic reconstruction based on the L1 gene reinforced the classification of both viruses within the Chipapillomavirus genus. A negative control processed alongside the samples yielded no papillomavirus reads, and no other positive samples were handled simultaneously, supporting the authenticity of the dual detection.

DNA extracted from the paraffin-embedded carcinoma was then tested by conventional PCR targeting a partial L1 gene segment, followed by bidirectional Sanger sequencing. The carcinoma tested positive for viral DNA, and the sequence matched CPV8 with 100 percent nucleotide identity to the genome recovered from the pigmented plaques. The absence of CPV9 in this assay likely reflects primer complementarity bias, since consensus primers can preferentially amplify one viral genome over another in mixed infections. The researchers note that high-throughput sequencing, by contrast, enabled unbiased recovery of both complete genomes, underscoring its superior sensitivity for detecting co-infections.

Therapeutically, the ulcerated lesions were surgically excised, and the remaining plaques were treated with topical imiquimod 5 percent cream applied once daily. After 21 days the dog showed an excellent clinical response, with complete resolution or flattening of most plaques, although adverse effects included skin depigmentation and a focal inflammatory burn-like reaction on one flank that resolved when treatment was paused. Imiquimod was restarted at a reduced frequency of twice weekly. Fourteen months after the initial presentation, most lesions remained well controlled, but a new ulcerated lesion appeared on the right side of the body, and histopathology confirmed carcinoma in situ. That later lesion could not be examined molecularly.

The authors emphasize that the malignant potential of these canine papillomaviruses remains hypothetical, and that the CPV DNA detected in the carcinoma could conceivably originate from superficial epithelium or adjacent viral plaques rather than from the tumor cells themselves. A limitation of the study is the absence of tissue localization methods such as in situ hybridization or immunohistochemistry, which could have strengthened the evidence. Nevertheless, the consistent detection of the same CPV8 strain in both the plaque and the carcinoma, using different methodologies, supports an association between viral infection and neoplastic progression in this case. The finding that both co-infecting viruses encode E6 and E7, oncogenes known in papillomaviruses to drive continuous replication of infected epithelial cells and disrupt critical cellular regulatory pathways, raises the hypothesis that co-infections within the Chipapillomavirus genus could contribute to squamous cell carcinoma development in some canine patients. Notably, this transformation occurred in a dog with no clinical or laboratory evidence of immunodeficiency, reinforcing the need to reconsider the oncogenic potential of canine papillomaviruses in naturally occurring disease and to investigate the host-virus interactions that may tip pigmented plaques toward cancer.

Subject of Research: Co-infection of canine papillomavirus types 8 and 9 in pigmented viral plaques concurrent with squamous cell carcinoma in a dog

Article Title: Case Report: Canine papillomavirus type 8 and 9 co-infection in pigmented viral plaques concurrent with squamous cell carcinoma in a Chinese crested dog

Article References: Baretta, L. T., Saueressig, A., Pereira, E. D. L., Pereira, V. M. A. G., Schuch, M., Filippi, M., Sita, A., Schons, J. G., Demoliner, M., de Camargo, L. J., Budaszewski, R. F., Weber, M. N., de Almeida, P. R., Daudt, C., da Silva, F. C., Santos, K. H. S., Canal, C. W., Spilki, F. R., Trevizan, L., & da Silva, M. S. (2026). Case Report: Canine papillomavirus type 8 and 9 co-infection in pigmented viral plaques concurrent with squamous cell carcinoma in a Chinese crested dog. Frontiers in Virology, 6, Article 1832666. https://doi.org/10.3389/fviro.2026.1832666

Image Credits: AI Generated

DOI: 10.3389/fviro.2026.1832666

Keywords: canine papillomavirus, CPV8, CPV9, co-infection, pigmented viral plaques, squamous cell carcinoma, E6 oncogene, E7 oncogene, rolling-circle amplification, high-throughput sequencing, veterinary dermatology, oncogenesis

The dog was referred to the Veterinary Clinic of the Faculty of Veterinary Medicine at the University of Tehran with a striking dermatological picture. It lived outdoors under unsanitary conditions with regular exposure to vegetation and soil, and it presented with diffuse hair loss, marked redness, itching and scaling across the skin of its back. Crucially, there was no ulceration or open wound, no lethargy and no loss of appetite, so systemic illness seemed unlikely and a complete blood count was not performed. The owner declined a skin biopsy, which meant the team could not obtain histopathological evidence of fungal invasion, a detail that would later shape how carefully the conclusions had to be framed. Hair plucks and skin scrapings were collected from the affected areas under sterile conditions and sent to the laboratory for fungal examination.

The initial diagnostic workup followed the standard playbook for suspected dermatophytosis, the superficial fungal infection of keratinized skin that is usually caused by organisms such as Microsporum canis, Microsporum gypseum or Trichophyton mentagrophytes. A Wood’s lamp examination was negative, and a direct microscopic examination of material treated with 10 percent potassium hydroxide also failed to reveal fungal elements. But the story changed when the samples were cultured on Sabouraud Dextrose Agar. After incubation at 28 degrees Celsius, colonies emerged that were creamy-brown and powdery with a colorless reverse surface. Lactophenol cotton blue staining of the growth revealed thin, septate hyphae studded with large, round, warty conidia, a morphological signature that immediately suggested the team was not dealing with a routine dermatophyte.

Seeking to probe the organism’s thermal behavior, the researchers subcultured the colonies onto blood agar and incubated them at 37 degrees Celsius, close to mammalian body temperature, for five days. The fungus produced creamy, dome-shaped, mucoid colonies under these conditions, and Giemsa staining revealed round-to-oval yeast-like cells with budding and point attachments when viewed under oil immersion at 100 times magnification. This dimorphic tendency, the ability to alter its appearance under different growth conditions, added another layer of complexity to the identification. Morphology alone could not settle the question, particularly since members of the family Chaetomiaceae, to which Corynascus belongs, are notorious for overlapping phenotypic features among closely related species. The team therefore turned to the laboratory’s molecular arsenal.

Genomic DNA was extracted from the isolate using a commercial fungal DNA extraction kit, and the internal transcribed spacer region of ribosomal DNA, comprising the ITS1 spacer, the 5.8S rRNA gene and the ITS2 spacer, was amplified with the universal primers ITS1 and ITS4. The polymerase chain reaction protocol began with denaturation at 94 degrees Celsius for three minutes, followed by 37 cycles of denaturation for 30 seconds, annealing at 60 degrees Celsius for 30 seconds and extension at 72 degrees Celsius for 30 seconds, with a final extension of eight minutes. The roughly 600-base-pair amplicon was then sequenced, and the resulting sequence was deposited in GenBank under accession number PV082530, making it publicly available for future comparisons by researchers anywhere in the world.

The sequence told a clear story. BLAST analysis showed 99.36 percent nucleotide similarity to reference sequences of Corynascus verrucosus and 99.34 percent similarity to a reference sequence of Corynascus sepedonium, a closely related species whose ITS region differs only marginally. To resolve the placement further, the researchers aligned their sequence with reference data from GenBank and constructed a maximum likelihood phylogenetic tree in MEGA7 using the Kimura two-parameter model with 1000 bootstrap replicates. The Iranian isolate fell squarely within the broader Corynascus lineage and clustered tightly with C. verrucosus sequences from different geographic regions, while reference sequences annotated as Myceliophthora, including Myceliophthora sepedonium and Myceliophthora verrucosa, occupied the same larger assemblage. The tree was rooted with Amesia atrobrunnea as the outgroup, and the resulting topology was consistent with previously published taxonomic frameworks placing Corynascus within the family Chaetomiaceae.

The taxonomy behind that placement is itself a story of scientific revision. The genus Corynascus comprises seven recognized species, and its boundaries have shifted repeatedly over decades of study, from early work by von Klopotek in 1974 and Stchigel and colleagues in 2000, who described three new thermotolerant species, to a 2015 re-evaluation of Myceliophthora using morphological and multilocus phylogenetic data that affirmed Corynascus as a distinct genus. More recent comprehensive studies have supported that distinction using multigene analyses incorporating ITS, LSU, rpb2, tub2 and tef sequences. Meanwhile, members of the Myceliophthora lineage have attracted industrial attention for their production of thermostable enzymes, and C. verrucosus itself made headlines in 2020 when researchers documented it as a mycoendophyte of Croton bonplandianus and a potential source of bioactive metabolites active against multidrug-resistant pathogens and cancer cells. None of this industrial or pharmacological relevance implies pathogenicity, a distinction the authors are careful to draw.

Where might a pet dog have encountered such a fungus? Environmental studies of composting offer a suggestive clue. Research on organic waste and manure composting has documented substantial shifts in fungal community composition as physicochemical conditions change, with thermophilic and thermotolerant fungi, exactly the ecological guild to which many Corynascus species belong, flourishing in these habitats. Composting environments and similar organic-material settings may therefore serve as reservoirs of environmentally adapted fungal taxa. The Tehran patient’s outdoor lifestyle, unsanitary surroundings and regular contact with soil and vegetation provided ample opportunity for exposure. Still, the authors emphasize that phylogenetic relatedness does not imply shared biological function or pathogenic potential, and that genetic similarity alone should never be read as evidence of a shared disease-causing role.

The clinical narrative, however, lends weight to a genuine association rather than a chance contaminant. The same fungal species was recovered on three independent cultures from the lesion, no bacterial growth was detected, and mite infestation was excluded. The dog was treated with oral ketoconazole combined with ketoconazole shampoo, receiving four weekly medicated baths. The itching and redness resolved within about a month, hair regrowth followed, and a uniform coat had returned approximately six months after treatment began. Over a nine-month follow-up period, the original cutaneous signs never recurred. The combination of repeated isolation, exclusion of other pathogens, molecular identification and clinical improvement following antifungal therapy supports, though it does not prove, a causal link.

That caution about proof is the intellectual heart of the report. Because histopathological examination was never performed, tissue invasion by the fungus could not be demonstrated directly, and the authors explicitly frame the finding as an association rather than definitive evidence of causality. Their broader message concerns method: for uncommon environmental fungi recovered from veterinary specimens, accurate identification demands a polyphasic approach that integrates morphology, ITS sequencing and phylogenetic placement rather than relying on any single line of evidence. Molecular methods can rescue isolates that fail to produce characteristic reproductive structures in culture, but they carry their own biases and limited discriminatory power, as the near-identical ITS sequences of C. verrucosus and C. sepedonium illustrate. By expanding the documented occurrence of C. verrucosus to a canine cutaneous lesion, the case adds a small but genuinely novel data point to veterinary mycology and a reminder that the fungal world’s opportunists may be more numerous, and better camouflaged, than current diagnostics routinely reveal.

Subject of Research: A rare case of cutaneous infection by the environmental fungus Corynascus verrucosus in a Shih Tzu dog, identified through molecular and phylogenetic analysis.

Article Title: A Rare Case of Cutaneous Infection by Corynascus verrucosus in a Shih Tzu Dog: Molecular Identification and Phylogenetic Analysis

Article References: Ghahremani, M., Sharifzadeh, A., Ashrafi Tamai, I., & Faridfar, G. (2026). A Rare Case of Cutaneous Infection by Corynascus verrucosus in a Shih Tzu Dog: Molecular Identification and Phylogenetic Analysis. Veterinary Medicine and Science, 12(5), Article e71205. https://doi.org/10.1002/vms3.71205

Image Credits: AI Generated

DOI: 10.1002/vms3.71205

Keywords: Corynascus verrucosus, veterinary mycology, canine dermatology, fungal infection, ITS sequencing, phylogenetic analysis, Chaetomiaceae, dermatophytosis, Shih Tzu, molecular identification, environmental fungi, ketoconazole treatment